(a) Field of the Invention
This invention relates to the art of constructing slopes and, more particularly to an improved method and apparatus for stabilizing fill slopes.
(b) Description of the Prior Art
In the process of building roads, highways, dams, embankments, etc., there is a requirement for stabilizing their slope surfaces, both when the slopes are initially constructed, and when the slopes are being reconstructed.
Relatively-flat earth fill surfaces are typically best stabilized with the use of well-known vibratory compactors. A typical such vibratory compactor comprises a main frame, a roller rotatably mounted on the frame, and an engine fixedly-mounted upright on the frame for driving the vibratory shaft of the roller. For relatively flat earth filled surfaces and for slopes less than two-to-one, the use of a vibratory compactor can produce the desired compaction effects, such as are prescribed in typical construction specifications.
However, it was generally believed by those skilled in the art that vibratory compactors could not be employed for compacting slopes, equal to or steeper than about two-to-one, hereinafter and in the claims called "regular slopes", which are the most widely used slopes. As a consequence, the outer surfaces of regular fill slopes are presently compacted much less than flat fill surfaces and fill slopes less than two-to-one, hereinafter sometimes called "irregular slopes". In other words, no commercially practical method is presently available for adequately compacting the outer surfaces of regular slopes.
In the construction or reconstruction of regular slopes, when the roller is first gradually released downslope, it will erode the fill material on the slope's surface. Then, when the same roller is pulled upslope over the eroded surface, it only slightly compacts the slope's fill material. The greater the number of downslope-upslope roller passes, the more a regular slope will erode, whereas on flat surfaces and on irregular slopes, the greater the number of passes, the greater the compaction effect becomes. Regular slopes are presently being treated with a non-vibratory roller, and are therefore not being compacted with a vibratory compactor.
The industry has of necessity standardized on the requirement that an average of about three complete roller passes, regardless of their respective compaction effects, will be accepted as meeting the lower compaction standards set for regular fill slopes, provided that the roller meets certain mechanical specifications, as to size, weight, etc.
For judging the compactness of flat earth fill surfaces, the criterion is typically expressed as a percentage, say 85 to 95%, of the maximum achievable on site compaction. While such high compaction effects are achievable with known vibratory compactors on flat earth fill surfaces and on the surfaces of irregular slopes (less than two-to-one), the compaction effects achievable on the outer surfaces of regular slopes (greater than two-to-one) are substantially less than 85%, typically say between 35% and 65% of maximum compaction.
This inferior achievable compaction is primarily responsible for the relatively rapid deterioration of regular slopes, especially in regions characterized by high winds and heavy rains. Millions of dollars are annually spent for the repair of slope-supported structures which are damaged as a result of eroded slopes, and for the reconstruction of the eroded slopes.
Additionally, the sloughed fill materials from eroding slopes frequently end up in streams and rivers, causing damage to wildlife, and polluting their waters, as well as adjacent agricultural fields.
It is a general object of my invention to provide a method and an apparatus for stabilizing regular slopes, i.e., two-to-one or greater, to substantially the same standards of compaction imposed by the construction industry on flat earth surfaces and irregular slopes, i.e., less than two-to-one, thereby eliminating the above described environmental problems caused by insufficiently compacted slopes, such as are produced with presently known earth fill compaction methods.